Methods and devices for establishing security associations in communications systems

ABSTRACT

A method of providing secure communications between a base station, a relay station, and a mobile station in a communication network includes authenticating the mobile station over the communication network; generating, by the base station, security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK); transmitting, by the base station, the security material to the mobile station; and transmitting, by the base station, the security material to the relay station.

PRIORITY

This application claims the benefit of priority of U.S. Provisional Application No. 60/969,773, filed Sep. 4, 2007; U.S. Provisional Application No. 60/981,767, filed Oct. 22, 2007; and U.S. Provisional Application No. 60/985,538, filed Nov. 5, 2007, all of which are incorporated by reference herein in their entirety for any purpose.

TECHNICAL FIELD

The present disclosure relates to the field of communications and, more particularly, to systems and methods for establishing security associations in a communication system.

BACKGROUND

Conventional wireless network environments connect mobile electronic devices to a service provider. More specifically, WiMAX (Worldwide Interoperability for Microwave Access) network environments connect a client device, through intermediate connections, to, for example, the Internet. WiMAX is a wireless networking technology that provides communication to wireless devices over significant distances. Authentication and reauthentication delays, however, can slow communication with the client device and decrease the efficiency of a WiMAX environment.

FIG. 1 is a block diagram of an exemplary prior art wireless communication system for use in an IEEE 802.16d/802.16e WiMAX wireless communication system. Access to Internet 100 is provided to at least one connectivity service network (CSN) 102, using at least one authentication, authorization, and accounting (AAA) server 104. CSN 102 is connected to gateways (GWs) 106 and 108. Gateways 106 and 108 are each a type of communication network authenticator and typically connected to several base stations (BSs) 110-115, the number of such BSs depending on network demands in a given area, though a gateway may instead be connected to only a single base station. Only two gateways 106 and 108 are shown, but it is possible to have greater or fewer gateways depending on the number of required base stations.

In FIG. 1, six base stations are shown as an exemplary WiMAX environment, but greater or fewer base stations may be provided depending on the number of available gateways and the network demands in the WiMAX environment. Base stations, such as base station 110 and base station 114, communicate with one or more client devices. Client devices include mobile stations (MSs), such as mobile stations 120, 122 and 124, to which the base stations provide wireless network service, and subscriber stations (SSs), such as subscriber stations 126 and 128, to which base stations provide wired or wireless network service. The network needs of several client devices may be satisfied by a single base station, and a single base station may satisfy the network needs of both mobile stations and subscriber stations.

In the conventional WiMAX environment, such as that shown in FIG. 1, each time mobile station 120 is initially served by a gateway, e.g., gateway 106, via an associated base station, e.g., base station 110, it is necessary to authenticate mobile station 120. Following such authentication, so long as mobile station 120 moves in areas that enable continued service via the original authenticating gateway, no further gateway authentication is required. However, if mobile station 120 moves to an area served by a different gateway, e.g., gateway 108, mobile station 120 is handed over to the different gateway, so that it is necessary for that different gateway to reauthenticate mobile station 120 as part of the handoff processing before service may be provided. After a client device has been authenticated or reauthenticated, security associations, or the sharing of security information between two network entities such as mobile station 120 and base station 110, are established to ensure that communications between the two entities are secure.

Authentication protocol standards have been created to standardize advance authentication techniques. These standardized protocols may include, for example, IEEE 802.1X authentication, extensible authentication protocol (EAP) method for global system for mobile communications (GSM) subscriber identity (EAP-SIM) and extensible authentication protocol method for universal mobile telecommunications systems (UMTS) authentication and key agreement (EAP-AKA) and/or a combination of the extensible authentication protocol (EAP) and the remote authentication dial in user service (RADIUS) protocol. In addition, standardized handshake protocols, such as security association signaling protocols, e.g., security association and traffic encryption key (SA-TEK) 3-way handshakes, and traffic encryption key (TEK) 3-way handshakes may be used to establish security associations over a communication link.

In IEEE 802.16d/802.16e WiMAX wireless communication systems, these standardized techniques are performed between a base station and a mobile station. Each standardized authentication technique requires multiple transmissions, which consume authentication time and processing overhead.

FIG. 2 is a signaling diagram of exemplary prior art authentication and authorization in an IEEE 802.16d and 802.16e WiMAX wireless communication system. An initialization process 200 is used to ensure that a mobile station requesting network service is authorized to access the network and to provide a security association between mobile stations and base stations to allow secure message transmission. For example, initialization process 200 may be used to provide a security association between mobile station 120 just after it moved into the range of base station 111 after previously being within the range of base station 110.

In the first step of initialization process 200, mobile station 120 is wirelessly connected to base station 111 through the link up process 202 which includes, for example, a ranging request and a ranging response. Mobile station 120 must then go through a multi-step process of authentication such as IEEE 802.1X full authentication 206 with AAA server 104 through gateway 106. Then AAA server 104 computes a master session key (MSK) 208 for mobile station 120 and transfers MSK 208 to gateway 106, which stores MSK 208 in its cache. The product of authentication through, for example, the EAP method or other authentication method is the transfer of MSK 208, which is known to AAA server 104, gateway 106, and mobile station 120. Gateway 106 will generate a pairwise master key (PMK) 210 and an authentication key (AK) 212 for mobile station 120, and transfer AK 212 to base station 111.

Mobile station 120 may also independently hold and store MSK 208 in its memory and may generate AK 212. Then base station 111 may perform the SA-TEK 3-way handshake procedure 214 to confirm that the AK held by mobile station 120 is the same AK 212 held by base station 111. Using AK 212, commonly held by base station 111 and mobile station 120, base station 111 and mobile station 120 may both respectively calculate a common message authentication code key (MACK) 224 and a common key encryption key (KEK) 220. MACK 224 may identify an authenticated message generated by mobile station 120 and base station 111. KEK 220 may protect transmission of traffic encryption keys from base station 120 to mobile station 111. Base station 110 and mobile station 120 may perform SA-TEK 3 way handshake procedure 214 using MACK 224 to authenticate each other. When SA-TEK 3-way handshake procedure 214 has been successfully completed, the base station 110 may generate a traffic encryption key (TEK) 222 and then carry out a TEK 3-way handshake procedure 216 with KEK 220 to establish security association with the mobile station 120. TEK 222 is typically randomly generated by the base station 111 and is used to encrypt data transmitted between mobile station 120 and base station 111 after mobile station 120 has been authenticated and authorized to access the network. SA-TEK 3-way handshake 214 and TEK 3-way handshake 216 are well-known in the art and will not be discussed further.

In initialization process 200 for use in IEEE 802.16d and 802.16e WiMAX wireless communication systems as shown in FIG. 2, base station 111 controls whether data transmission occurs over the channel between base station 111 and mobile station 120 because base station 111 and mobile station 120 both hold the same TEK 222, KEK 220, and AK 212, from which MACK 224 can be derived. After mobile station 120 has established a security association with base station 111, or, in other words, after mobile station 120 has been granted permission to communicate over the network, encrypted data transmission occurs between mobile station 120 and base station 111 using TEK 222.

Referring again to FIG. 1, in operation, the strength of the signal and transmission quality may decrease as the network signal travels from gateway 106 or gateway 108 to base stations 110-115 to client devices 120, 122, 124, 126, and 128. Additionally, the signal and transmission quality decrease as a mobile station travels further from its serving base station. Signal quality and coverage may also be affected by factors such as physical structures, signal interferences, weather and transmission conditions and formats. Therefore, coverage gaps or holes may exist and users in those areas may have limited or no network access.

One solution to avoid or reduce coverage gaps is to provide more base stations, but this solution can be costly. Alternatively, a network may avoid or reduce coverage gaps and/or extend its network coverage by using relay stations (RSs), such as those implementing the concept of multi-hop relaying (MR) as set forth in IEEE 802.16j. Base stations communicate with these relay stations, which boost and relay signals to and from mobile stations and base stations, but otherwise are not involved in authentication and/or establishing security associations.

FIG. 3 is a block diagram of an exemplary prior art wireless communication system for use in an IEEE 802.16j WiMAX wireless communication system with MR architecture. Similar to the IEEE 802.16d and 802.16e WiMAX wireless communication systems, access to Internet 100 is provided through at least one AAA server, such as AAA server 104, and via at least one gateway, such as gateway 106. For convenience, Internet 100, CSN 102, AAA server 104 and gateway 106 are referred to as core network 300. Network 300, and specifically, gateway 106, typically communicates with base stations 310-313 over a wired connection.

Four base stations 310-313 are shown in FIG. 3, but greater or fewer base stations may be provided. Base stations, such as base station 310, may communicate directly with one or more mobile stations, such as mobile station 320, via wireless transmission. Base stations, such as base station 311 and base station 312, may communicate indirectly with one or more mobile stations, such as mobile stations 322, 324, and 326. Base stations typically communicate with one or more relay stations, such as relay stations 328, 330, and 332, via wireless transmission, but they may also communicate over wired connections. Relay stations 328, 330, and 332 boost and relay the signal to/from mobile station 322 via wireless transmission. As shown, relay stations 328, 330, and 332 are fixed relay stations. However, base stations may also communicate with mobile relay stations (MRSs), such as mobile relay station 334. A mobile relay station could reside, for example, on a train, plane or automobile and provide its passengers having mobile stations with mobile network access to various base stations and/or relay stations as the mobile relay station travels. As shown in FIG. 3, mobile relay station 334 provides wireless service to mobile stations 324 and 326, but the network needs of only one mobile station, or several mobile stations, may be satisfied by a single mobile relay station. Although not shown, base stations, such as base stations 310-313, may also communicate with one or more subscriber station. The network needs of several client devices, therefore, may be satisfied by a single base station either directly or through one or more relay stations. Moreover, relay stations 328, 330, and 332 may provide wireless service to additional relay stations, additional mobile relay stations, and/or additional mobile stations.

In some applications, the use of relay stations may increase the need for station-to-station (base/relay) handoffs and may require increased processing overhead for such handoffs due to the limited coverage areas of each relay station (including mobile relay stations). In addition, when secure communications are involved, the handoff process from one base/relay station to another base/relay station may require additional overhead and reduce efficiency, bandwidth, or quality of the communication connection.

The disclosed embodiments are directed to overcoming one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to a method of providing secure communications between a base station, a relay station, and a mobile station in a communication network. The method authenticates the mobile station over the communication network, and generates, by the base station, security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK). The method also transmits, by the base station, the security material to the mobile station. In addition, the method transmits, by the base station, the security material to the relay station.

In another aspect, the present disclosure is directed to a base station for providing secure communications in a communication network. The base station includes at least one memory to store data and instructions, and at least one processor configured to access the memory. The at least one processor is configured to, when executing the instructions, authenticate a mobile station over the communication network, and generate security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK). The at least one processor is further configured to cause transmission of the security material to the mobile station, and cause transmission of the security material to a relay station.

In another aspect, the present disclosure is directed to a relay station for providing secure communications in a communication network. The relay station includes at least one memory to store data and instructions, and at least one processor configured to access the memory. The at least one processor is configured to, when executing the instructions, cause transmission of a mobile station verification request to a base station in response to a ranging request from at least one mobile station and perform secure data transmission with the at least one mobile station using security material received from the base station, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK).

In yet another aspect, the present disclosure is directed to a system for providing secure communications. They system includes a base station configured to provide access to a communication network, authenticate at least one mobile station over the network, generate security material and transmit the security material. The system also includes a relay station in communication with the base station for receiving the security material and for providing secure data transmissions to the at least one mobile station using the security material. The security material includes at least one of a traffic encryption key (TEK) and a message authentication code key (MACK).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary prior art wireless communication system for use in an IEEE 802.16d/802.16e WiMAX wireless communication system.

FIG. 2 is a signaling diagram of exemplary prior art authentication and authorization in an IEEE 802.16d and 802.16e WiMAX wireless communication system.

FIG. 3 is a block diagram of an exemplary prior art wireless communication system for use in an IEEE 802.16j wireless communication system with multi-hop relaying architecture.

FIG. 4 is a block diagram of an exemplary wireless communication system for use in an IEEE 802.16j wireless communication system in which selected relay stations serve as authenticator relay-relay stations.

FIG. 5 a is a block diagram illustrating an exemplary construction of a base station.

FIG. 5 b is a block diagram illustrating an exemplary construction of a mobile station.

FIG. 5 c is a block diagram illustrating an exemplary construction of a relay station or mobile relay station.

FIG. 6 is a signaling diagram of exemplary authentication and authorization in an 802.16j wireless communication system in which relay stations serve as authenticator relay-relay stations.

FIG. 7 is a signaling diagram of an exemplary handoff from a current authenticator relay-relay station to a target authenticator relay-relay station where both authenticator relay-relay stations communicate with the same base station.

FIG. 8 is a signaling diagram of an exemplary handoff from an authenticator relay-relay station connected to a current base station to a target connected to a different, target base station.

FIG. 9 is a signaling diagram of an exemplary mobile relay station handoff between a current base station and a target base station.

DETAILED DESCRIPTION

Embodiments of the disclosure can provide such security associations in IEEE 802.16j WiMAX wireless communication systems or other wireless communication networking systems that employ relay stations. By providing a relay station with the ability to establish a secure connection with mobile stations and provide mobile stations with access to network 300, processing overhead can be significantly reduced. Specifically, by providing a relay station with traffic encryption key and/or a message authentication key corresponding to a mobile station seeking access to the network 300, the relay station can establish a security association with the mobile station and perform mobile station authentication and authorization.

FIG. 4 is a block diagram of an exemplary wireless communication system for use in an IEEE 802.16j WiMAX wireless communication system in which selected relay stations serve as authenticator relay-relay stations (AR-RSs). In FIG. 4, a base station 400 is connected over a wire to network 300 and communicates wirelessly with one or more relay stations 402 and 404, which boost and relay the received signal to AR-RSs 406-409. As shown in FIG. 4, AR-RS (MRS) 408 is a mobile relay station. A security zone key, also called a relay key (RK) 410 is distributed by base station 400 to relay stations 402 and 404, and AR-RSs 406-409 after relay stations 402 and 404, and AR-RSs 406-409 are authenticated during their initialization to network 300 and is used to provide data and signal protection for the communication channels between relay stations and/or between relay stations and base stations in an IEEE 802.16j network. Relay stations 402 and 404 and/or base station 400 may perform data and signal encryption, decryption and message authentication using relay key 410. The area of network coverage provided by base station 400, relay stations 402 and 404, and AR-RSs 406-409 that share relay key 410 is called a secure relay zone (SRZ) 412. FIG. 4 illustrates a single mobile station 414 served by AR-RS 406 and two mobile stations 416 and 418 are served by AR-RS (MRS) 408, but the network needs of several mobile stations may be provided by a single AR-RS. In addition, although only AR-RS 408 is shown as a mobile relay station, additional AR-RSs within SRZ 412 may be mobile relay stations.

Each time mobile station 414 is initially served by base station 400, it is necessary to establish a security association with network 300. So long as mobile station 414 moves within SRZ 412, it may be possible to bypass further security association establishment and authentication. However, if mobile station 414 moves to an area served by a different base station, mobile station 414 is handed over to the different base station, so that it may be necessary for that different base station to establish another security association with mobile station 414, and, depending upon whether the different base station is connected through gateway 106, authenticate mobile station 414 as part of the handoff processing. Such reauthentication and/or security association establishment introduces delay in providing service to mobile station 414.

FIG. 5 a is a block diagram illustrating an exemplary construction of a base station such as base station 400. Base station 400 may be any type of communication device configured to transmit and/or receive data and/or communications to and from one or more mobile stations such as mobile station 414, relay stations such as relay stations 402 and 404, and/or AR-RSs such as AR-RSs 406-409, in a wireless communication system. As shown in FIG. 5 a, each base station 400 may include one or more of the following components: at least one central processing unit (CPU) 500 configured to execute computer program instructions to perform various processes and methods, random access memory (RAM) 502 and read only memory (ROM) 504 configured to access and store information and computer program instructions, memory 506 to store data and information, database 508 to store tables, lists, or other data structures, I/O devices 510, interfaces 512, antennas 514, etc. Each of these components is well-known in the art and will not be discussed further.

FIG. 5 b is a block diagram illustrating an exemplary construction of a mobile station such as mobile station 414. As shown in FIG. 5 b, each mobile station 414 may include one or more of the following components: at least one CPU 520 configured to execute computer program instructions to perform various processes and methods, RAM 522 and ROM 524 configured to access and store information and computer program instructions, memory 526 to store data and information, database 528 to store tables, lists, or other data structures, I/O devices 530, interfaces 532, antennas 534, etc. Each of these components is well-known in the art and will not be discussed further.

FIG. 5 c is a block diagram illustrating an exemplary construction of a relay station or mobile relay station such as AR-RS/mobile relay station 406. As shown in FIG. 5 c, each relay station/mobile relay station 406 may include one or more of the following components: at least one CPU 540 configured to execute computer program instructions to perform various processes and methods, random access memory RAM 542 and read only memory ROM 544 configured to access and store information and computer program instructions, memory 546 to store data and information, database 548 to store tables, lists, or other data structures, I/O devices 550, interfaces 552, antennas 554, etc. Each of these components is well-known in the art and will not be discussed further.

FIG. 6 is a signaling diagram of exemplary authentication and authorization in an IEEE 802.16j WiMAX wireless communication system in which selected relay stations serve as authenticator relay-relay stations. An initialization process 600 is used to ensure that a mobile station requesting network service is authorized to access network 300 and to provide a security association between mobile stations, relay stations and AR-RSs for secure message transmission. For example, process 600 may be used to authenticate and establish a security association with mobile station 414 just after it is turned on, or after it has moved into the coverage area provided by AR-RS 406 from a coverage area provided through a base station connected to gateway 108.

At an initial link up 602, mobile station 414 sends a ranging request to AR-RS 406 indicating the presence of mobile station 414 in the area of coverage for AR-RS 406. AR-RS 406 responds by sending a ranging response to mobile station 414 to recognize the presence of mobile station 414 in its coverage area. AR-RS 406 sends an Authentication Request 604, protected by relay key 410, to base station 400. Authentication Request 604 informs base station 400 of the identification information of mobile station 414 that is served by AR-RS 406. Because mobile station 414 has not previously or recently been connected to network 300 through base station 400 and gateway 106, mobile station 414 authenticates with AAA server 104 using IEEE 802.1X full authentication protocol 206. AAA server 104 and mobile station 414 will each calculate a master session key (MSK) 606 when IEEE 802.1X full authentication 206 has been successfully completed. Then AAA server 104 transfers MSK 606 to gateway 106. Upon receiving MSK 606, gateway 106 calculates PMK 608 using MSK 606 and stores PMK 608 in its cache. Gateway 106 then computes AK 610 from PMK 608, and sends AK 610 to base station 400. Upon obtaining AK 610, base station 400 derives security material, such as KEK 612 and MACK 616 from AK 610. The MSK 606 is known to the AAA server 104, the gateway 106, and a client device such as mobile station 414. Mobile station 414 therefore independently hold MSK 606 and may derive PMK 608 and AK 610 and also derive the same MACK 616 and KEK 612. A client device such as mobile station 414 caches PMK 608 in its memory upon successful authentication using, for example, the EAP method. At this point, base station 400 and mobile station 414 perform SA-TEK 3-way handshake procedure 214 with MACK 616 to authenticate each other. When SA-TEK 3-way handshake procedure 214 is successfully completed, base station 400 will generate security material, including traffic encryption key (TEK) 614, first and then send the security material (e.g. TEK 614), protected by KEK 612, to mobile station 414. In one embodiment, TEK 614 is randomly generated by base station 400 and is used to provide data confidentiality between base station 400 and AR-RS 406. At the same time, base station 400 also delivers security material, which may include TEK 614 and MACK 616, protected by relay key 410, to AR-RS 406. Relay station 406 may receive MACK 616 to authenticate mobile station 414 directly and receive TEK 614 to encrypt/decrypt encrypted messages transmitted to and/or from mobile station 414. One or more security keys, such as MK, MSK 606, PMK 608, AK 610, KEK 612, TEK 614, MACK 616 may be referred to as security material.

AR-RS 406 may switch the communication channel between mobile station 414 and AR-RS 406 to an authorized state to provide mobile station 414 with access to network 300. Moreover, because mobile station 414 and AR-RS 406 have TEK 614, they may exchange encrypted data transmissions. Specifically, TEK 614 may then be used to encrypt the data transmitted between AR-RS 406 and mobile station 414 after mobile station 414 has been authenticated. If multicast service, where a base station may send messages to multiple client devices simultaneously, is available, BS 400 will also distribute a multicast key, which protects such multicast transmissions, to AR-RS 406 to enable MS 414 to receive transmissions intended for multiple mobile stations.

FIG. 7 is a signaling diagram of an exemplary handoff from a current AR-RS, for example AR-RS 406, to a target AR-RS, for example AR-RS 407, where the current AR-RS and target AR-RS each communicate with the same base station, e.g., base station 400. In FIG. 7, a link 702 is created between mobile station 414 and AR-RS 407 when mobile station 414 transmits a ranging request to AR-RS 407 including a security material identification such as an authentication key identification (AKID) and AR-RS 407 responds with a ranging response. The AKID identifies the AK currently stored in a memory (e.g., memory 526, ROM 524, RAM 522 or database 528) of mobile station 414 due to mobile station 414's prior authentication with AR-RS 406. AR-RS 407 transmits the AKID to base station 400 in an AK verification signal request 704 to verify that the AK stored in mobile station 414 matches the AK stored in the memory of base station 400 (e.g., memory 506, ROM 504, RAM 502 or database 508). Because AR-RS 406 and AR-RS 407 are within SRZ 412, they share the same relay key 410. As such, verification signal request 704 is encrypted using relay key 410 for security purposes. In one exemplary embodiment, because mobile station 414 has previously performed full authentication with base station 400 through AR-RS 406, the security material in base station 400 and mobile station 414 match (here, both AK 610). If the AKs match, base station 400 transmits an AK Verification Success message 706 to AR-RS 407; if the AKs do not match, base station 400 transmits an AK Failure message to AR-RS 407. In one exemplary embodiment, mobile station 414 may be programmed to transmit out an Extensible Authentication Protocol over Local Area Network (EAPOL)-Start message 708 to trigger IEEE 802.1X full authentication 206. When AR-RS 407 receives this start message, AR-RS 407 may skip IEEE 802.1X full authentication 206 by sending to mobile station 414 an EAPOL-Success message 710, thereby indicating that authentication was successful without going through the IEEE 802.1X full authentication protocol 206.

At this point, both base station 400 and mobile station 414 may hold the same security material such as AK 610. Mobile station 414 and base station 400 may each derive MACK 616 from AK 610. Mobile station 414 and base station 400 may hold previously calculated TEK 614 and/or previously generated KEK 612 and may perform SA-TEK 3-way handshake 214 to authenticate each other directly. Alternatively, as described above in connection with FIG. 6, base station 400 may generate a new KEK 712 by using AK 610 and may generate a new TEK 714. Base station 400 encrypts TEK 714 (or TEK 614) using KEK 712 (or TEK 612) and transmits encrypted TEK 714 (or TEK 614) to mobile station 414 for data confidentiality.

Base station 400 immediately sends security material such as TEK 714 (or 614) and MACK 616, protected using relay key 410, to AR-RS 407. After AR-RS 407 obtains TEK 714 (or 614) and MACK 616, AR-RS 407 may switch the communication channel between mobile station 414 and AR-RS 407 to an authorized state to provide mobile station 414 with access to network 300. Moreover, because mobile station 414 and AR-RS 407 then each have TEK 714 (or 614) and MACK 616, they may send encrypted data transmissions.

FIG. 8 is a signaling diagram of an exemplary handoff from an AR-RS connected to a current base station, e.g., AR-RS 407 connected to base station 400, to a target AR-RS 802 connected to a different, target base station 804. In FIG. 8, mobile station 414 sends link up message 702 including a security material identification such as AKID to target AR-RS 802. AKID identifies AK 610 currently stored in the memory of mobile station 414 (e.g., memory 526, ROM 524, RAM 522 or database 528) due to prior authentication with AR-RS 407. Target AR-RS 802 transmits the AKID to target base station 804 in AK verification signal request 704 to verify that the AK stored in mobile station 414 matches the AK stored in the memory of target base station 804 (e.g., memory 506, ROM 504, RAM 502 or database 508). Target AR-RS 802 is not in communication with the same base station as AR-RS 407, and as such does not share the same relay key 410, but rather target AR-RS 802 and target base station 804 share a new relay key 806. AK verification signal request 704 is therefore encrypted by AR-RS using new relay key 806. If the AK present at target base station 804 matches the AK within the memory of mobile station 414 (e.g., memory 526, ROM 524, RAM 522 or database 528), target base station 804 will transmit an AK Verification Success message to target AR-RS 806; if the AKs do not match or either target base station 804 or mobile station 414 do not hold an AK, target base station 804 transmits an AK Verification Failure message 808 to target AR-RS 802. In the exemplary embodiment shown in FIG. 8, because mobile station 414 was previously authenticated through base station 400, either the AK held by mobile station 414, AK 610, does not match that held by target base station 804 or target base station 804 does not have any AK corresponding to mobile station 414 so that target base station 804 transmits AK Verification Failure message 808 to mobile station 414. Upon receipt of AK Verification Failure message 808, mobile station 414 undergoes IEEE 802.1X full authentication 206 with AAA server 104, obtains a new MSK 810, a new PMK 812, and a new AK 814 from target base station 804.

When both target base station 804 and mobile station 414 have new AK 814, they will derive MACK 820 and KEK 816 from AK 814 and perform SA-TEK 3-way handshake procedure 214 to authenticate each other. When SA-TEK 3-way handshake procedure 214 is successfully completed, the base station 804 may generate a new TEK 818 and transmit new TEK 818 or old TEK 712, protected by KEK 816 to mobile station 414 for data confidentiality between mobile station 414 and relay station 407.

Target base station 804 will also send the TEK 818 and MACK 820, protected by new relay key 816, to target AR-RS 802. After target AR-RS 802 obtains TEK 818 and MACK 820, it may switch the communication channel between mobile station 414 and target AR-RS 802 to the authorized state to provide mobile station 414 with access to the network 300. Moreover, because mobile station 414 and target AR-RS 802 then each have TEK 816 and MACK 802, they may communicate using encrypted data transmissions.

Although the processes described above for initialization and handoffs apply to mobile relay stations as well, mobile relay stations and the mobile stations accessing the network from within mobile relay stations must also be prepared for a change in base station where the AR-RS (specifically, the mobile relay station) does not change.

FIG. 9 is a signaling diagram of an exemplary mobile relay station handoff between a current base station and a target base station. In FIG. 9, mobile relay station AR-RS 408 may associate with a target base station 900 when AR-RS 408 has moved or is about to move into the coverage area for target base station 900. Mobile stations 416 and 418 are connected to AR-RS 408 and their connection with AR-RS 408 is preferably maintained throughout the transition to target base station 900. In order to update the AKs of mobile stations 416 and 418, AR-RS 408 may issue a ranging message 902 prior to sending the mobile stations 416 and 418 to alert mobile stations 416 and 418 of the necessity of updating their security material because AR-RS 408 is within or approaching the coverage area for target base station 900. Upon receipt of security material update message 902, AR-RS 408 undergoes one or more of IEEE 802.1X authentication 206, SA-TEK 3-way handshake 214, and TEK 3-way handshake 216 with gateway 106 and AAA 104. As such, AR-RS 408 must receive an AK and be authenticated in a similar manner to authentication of a mobile station. Gateway 106 may transfer the AK for the mobile relay station at an AK Transfer 904.

AR-RS 408 transmits a re-authentication trigger message, or security material update message, 906 to mobile stations 416 and 418. The re-authentication trigger message 906 may be sent in a multicast transmission to mobile stations 416 and 418. Upon receipt of the re-authentication trigger message 906, the mobile stations 416 and 418 perform IEEE 802.1X full authentication 206 with gateway 106 and AAA server 104. Gateway 106 may calculate a new AK obtained from the existing PMK in the gateway for target base station 900. Gateway 106 and/or AAA server 104 may transfer all of the security material, such as AKs, for the mobile stations associated with AR-RS 408 to target base station 900 at an AK Transfer 908, and may do so in a tunnel mode, in which all of the parameters (e.g., AKs) of all mobile stations connecting to AR-RS 408 are transmitted at one time. In tunnel mode, the logical connection between two nodes, e.g., AR-RS 408 and gateway 106 is dedicated, and intermediate nodes do not process the tunnel packets but rather only forward them on. Mobile stations 416 and 418 then undergo SA-TEK 3-way handshake 214 with target base station 900. Target base station 900 will provide security material such as TEKs and MACKs for each of the mobile stations to AR-RS 408 at a TEK Transfer 910, and may do so using tunnel mode. In one embodiment, target base station 900 will aggregate security material and send security material for each of the mobile stations to AR-RS 408 at TEK Transfer 910 in a message aggregation mode. In one embodiment, the TEKs and MACKS are received at base station 900 and mobile stations 416 and 418 prior to the inter-base station handoff to avoid a disconnect in service to mobile stations 416 and 418. AR-RS 408 may then provide secure data transmission to the mobile stations 416 and 418 and may do so without performing an authentication procedure with mobile stations 416 and/or 418. In addition, AR-RS 408 may update only authentication data within the mobile stations 416 and 418 and, in some embodiments, may not change the traffic encryption key (TEK) held by the mobile stations 416 and/or 418.

One of skill in the art will appreciate that although FIG. 9 shows target BS 900 communicating with the network and AAA server 104 via gateway 106, target base station 900 may also communicate with the network and AAA server 104 via gateway 108, or another gateway, with the same processing as described in FIG. 9.

Systems and methods disclosed herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Apparatus embodying the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor. Method steps consistent with the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on the basis of input data, and by generating output data. Embodiments consistent with the invention may be implemented in one or several computer programs that are executable in a programmable system, which includes at least one programmable processor coupled to receive data from, and transmit data to, a storage system, at least one input device, and at least one output device, respectively. Computer programs may be implemented in a high-level or object-oriented programming language, and/or in assembly or machine code. The language or code can be a compiled or interpreted language or code. Processors may include general and special purpose microprocessors. A processor receives instructions and data from memories. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by or incorporated in ASICs (application-specific integrated circuits).

It will be apparent to those skilled in the art that various modifications and variations can be made in the system and method for establishing security associations in wireless communications systems. For example, one of skill in the art will appreciate that ranging requests and responses are a type of signaling message and that other signaling messages may be used. In addition, one of skill in the art will appreciate that traffic encryption keys are a type of traffic key and that other traffic keys may be used, and that MACKs are a type of verification key and that other verification keys may be used. One of skill in the art will also appreciate that communication between base stations and relay stations can be wireless or wired. It is intended that the standard and examples be considered as exemplary only, with a true scope of the disclosed embodiments being indicated by the following claims and their equivalents. 

1. A method of providing secure communications between a base station, a relay station, and a mobile station in a communication network, the method comprising: authenticating the mobile station over the communication network; generating, by the base station, security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK); transmitting, by the base station, the security material to the mobile station; and transmitting, by the base station, the security material to the relay station.
 2. The method of claim 1, further comprising transmitting, by the base station, secured communications to the mobile station using the security material.
 3. The method of claim 1, wherein the authenticating includes performing secure authentication.
 4. The method of claim 3, wherein the authenticating includes performing IEEE 802.1X authentication.
 5. The method of claim 1, wherein the authenticating comprises receiving, at the base station, an authentication key (AK) from a communication network authenticator, wherein the security material is generated using the AK, and wherein the security material does not include the AK.
 6. The method of claim 1, wherein the authenticating comprises receiving, at the base station, a security material identification from the mobile station, the security material identification corresponding to an authentication key (AK) stored in the mobile station, transmitting, by the base station, a verification success message to the mobile station if the base station recognizes the AK, and requiring the mobile station to perform IEEE 802.1X full authentication if the base station does not recognize the AK.
 7. The method of claim 1, further comprising establishing a secure communication path between the base station and the relay station, wherein the base station transmits the at least one security material to the relay station over the secure communication path.
 8. The method of claim 1, wherein communication between the base station and the relay station is wireless.
 9. A base station for providing secure communications in a communication network, the base station comprising: at least one memory to store data and instructions; and at least one processor configured to access the memory and configured to, when executing the instructions: authenticate a mobile station over the communication network; generate security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK); cause transmission of the security material to the mobile station; and cause transmission of the security material to a relay station.
 10. The base station of claim 9, wherein executing the instruction to authenticate includes performing secure authentication.
 11. The base station of claim 10, wherein executing the instruction to authenticate includes performing IEEE 802.1X authentication.
 12. The base station of claim 9, wherein executing the instruction to authenticate includes receiving, at the base station, an authentication key (AK) from a communication network authenticator, wherein the security material is generated using the AK, and wherein the security material does not include the AK.
 13. The base station of claim 9, wherein executing the instruction to authenticate includes receiving, at the base station, a security material identification from a mobile station, the security material identification corresponding to an authentication key (AK) stored in the mobile station, transmitting, by the base station, a verification success message to the mobile station if the base station recognizes the AK, and requiring the mobile station to perform IEEE 802.1X full authentication if the base station does not recognize the AK.
 14. The base station of claim 9, wherein the at least one processor is further configured to establish a secure communication path between the base station and the relay station, and to transmit the security material to the relay station over the secure communication path.
 15. The base station of claim 9, wherein communication between the base station and the relay station is wireless.
 16. A relay station for providing secure communications in a communication network, the relay station comprising: at least one memory to store data and instructions; and at least one processor configured to access the memory and configured to, when executing the instructions: cause transmission of a mobile station verification request to a base station in response to a ranging request from at least one mobile station; and perform secure data transmission with the at least one mobile station using security material received from the base station, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK).
 17. The relay station of claim 16, wherein the at least one processor is further configured to establish a secure communication path between the base station and the relay station, and wherein the relay station transmits the verification request to the base station over the secure communication path.
 18. The relay station of claim 16, wherein the relay station is a mobile relay station.
 19. The relay station of claim 18, wherein the at least one processor is further configured to cause transmission of a security material update message to the at least one mobile station to alert the at least one mobile station to update its security material.
 20. The relay station of claim 19, wherein the transmission of the security material update message to the at least one mobile station is a multicast transmission.
 21. The relay station of claim 16, wherein communication between the relay station and the base station is wireless.
 22. A system for providing secure communications, the system comprising: a base station configured to provide access to a communication network, authenticate at least one mobile station over the network, generate security material and transmit the security material; and a relay station in communication with the base station for receiving the security material and for providing secure data transmissions to the at least one mobile station using the security material, wherein the security material comprises at least one of a traffic encryption key (TEK) and a message authentication code key (MACK).
 23. The system of claim 22, wherein the relay station is a mobile relay station.
 24. The system of claim 23, wherein the base station aggregates the security material and transmits the aggregated security material to the relay station.
 25. The system of claim 23, wherein the relay station provides the secure data transmissions to the at least one mobile station using the security material without performing an authentication procedure with the at least one mobile station.
 26. The system of claim 23, wherein the relay station provides the secure data transmissions to the at least one mobile station using the security material but without changing the traffic encryption key (TEK) held by the at least one mobile station.
 27. The system of claim 22, wherein communication between the base station and the relay station is wireless. 